Condition-dependent auditory function and reproductive development in the round goby, Neogobius melanostomus

Neural responses to sensory stimuli often differ between sexes and can be regulated by endocrine activity. This thesis examines the effects of sex, reproductive condition, female plasma 17b-estradiol level, and saccule hair cell density on auditory function in the round goby (Neogobius melanostomus). Relative to males, females had greater auditory sensitivity in the upper range of their hearing (300-600 Hz) and a higher density of hair cells. Female 17b-estradiol was associated with changes in auditory filtering properties at low frequencies (100-200 Hz). Additionally, I examined associations between gonadosomatic index, reproductive hormones, and stage of gonadal development in the round goby. Gonadasomatic indices provided limited resolution on reproductive condition in males and females; these categories encompassed individuals in varied endocrine and gonadal conditions. The results demonstrate auditory sexual dimorphism, elucidate the physiological mechanisms regulating auditory function, and present a framework for future studies on the reproductive cycle in the round goby

Condition-dependent auditory processing in the round goby (Neogobius melanostomus): Links to sex, reproductive condition and female estrogen levels

Neural responses to sensory stimuli often differ between sexes, vary seasonally, and can be regulated by endocrine activity, but the ecological and physiological mechanisms driving such patterns are not well understood. The current study examined how auditory function in the round goby (Neogobius melanostomus), a vocal teleost, co-varied with sex, reproductive condition and female plasma 17β-estradiol level. Auditory evoked potentials were collected in response to tone pips (100–600Hz) and a natural round goby pulse vocalization. Additionally, saccule hair cell densities were compared across reproductive groups. Auditory threshold was evaluated in terms of pressure and particle acceleration, and response amplitude and onset latency were measured at 10dB above threshold. Relative to males, females displayed lower auditory thresholds in response to the natural vocalization and to tones at 300–600Hz, and had a higher density of saccule hair cells. The 17β-estradiol level was positively associated with amplitude and latency for the pulse stimulus and with both threshold and amplitude for tones at 100–200Hz in females. Relative to non-reproductive males, reproductive males exhibited longer response latencies at 100–200Hz. The results demonstrate sexual dimorphism in auditory function in a teleost fish as well as intra-sexual variation, partially based on hormone levels. The current research further identifies links between auditory function and reproductive behaviors in fishes and provides a finer-scaled analysis of how this behavior is reflected at the level of the sensory systems facilitating signal reception